The current research on carbon sequestration in plant communities within urban green spaces should shift from focusing on individual plant indices to considering the community as a whole. In this study, the plant communities of 13.5 hm2 of green land located in the middle section of the north bank of the Weihe River in Xixian New Area were examined. The annual carbon sequestration, carbon storage, and functional diversity of different vegetation types within communities were assessed, and correlation analysis and multiple-step regression analysis were conducted. The results showed that the average height and diameter of the tree layer were positively correlated with annual carbon sequestration (p<0.05). The average height of the shrub community was positively correlated with annual carbon sequestration (p<0.05). The average height, leaf area, and leaf area index of the meadow ground cover community were positively correlated with the annual carbon sequestration (p<0.01). The average leaf area index can fit the annual carbon sequestration of the forest land community, and the annual carbon sequestration of the meadow ground cover community can be fitted by the average community height and leaf area index. The increase of community carbon sink is more dependent on the traits of dominant species than on the complementary effects of diversity. The high carbon sequestration plant community allocation model with three planting covers was proposed. The annual carbon sequestration of the forest community was 10.25 t/hm2, and that of the meadow ground was 21.6 kg/m2. The research results offer a quantitative design paradigm for enhancing the quality and efficiency of urban green space carbon sinks, providing theoretical support and practical guidance for achieving low-carbon cities and sustainable development.